Light relay



Nov. 10, 1936. R. c. HITCHCOCK 2,060,500

LIGHT RELAY Filed March 50, 1954 2 Sheets-Sheet 1 Fig.4.

INVENTOR BcharaG H'ichcocfi,

' I AT NEY Patented Nov. 10, 1936 UNITED STATES PATENT OFFICE LIGHT RELAY of Pennsylvania Application March 30, 1934, Serial No. 718,282

5 Claims.

My invention pertains to a light and contact control relay and more particularly to an electronic control device which is extremely sensitive and stable in its operation.

A majority of the light relays on the market operate on alternating current, the associated contactor coil being supplied with pulsating direct current by the self rectification of the amplifier tube. Usually the grid circuit also operates on alternating current, thus the length of the control grid wires is very limited because of capacity eifects. With a photo-cell lead of over ten feet the capacity charging current often exceeds the photo-electric current. Adequate shielding is impossible without impracticably large cables. Even when these effects can be compensated, the grid condensers, and frequently others, have to be changed for each different supply frequency.

It is an object of my invention to provide a relay control device which though responsive to very'ieeble control currents is sufficiently stable for commercial installations where the conductors must be extended an appreciable distance to the photo-cell or other control member.

It is a further object of my invention to provide a light and contact relay device which can be energized from an alternating current source of any frequency.

It is also an object of my invention to provide a light-contact control relay wherein fast or slow action may be had either on making or breaking a light beam or contact.

Another object of my invention is to provide a light-contact control device with a panel which allows the user to conveniently make connections for obtaining relay operation on either making or breaking the light beam or contact.

A further object of my invention is to provide a simple unit in which a control relay is actuated directly from a photo-cell or other feeble device thereby eliminating the usual telephone relay. 2

More specifically, it is an object of my invention to provide a simple, sensitive, stable control unit wherein an electromagnetic switch with a contact rating of 20 amperes is controlled by a feeble control current of the order of 10 microamperes.

The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments, when read in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic view illustrating an embodiment of my invention utilizing a triode and a voltage doubling rectifier arrangement for applying independently rectified voltages to the anode and the control electrodes.

Figs. 2, 3 and 4 are similar views showing modifications of my invention;

Fig. 5 is a perspective view showing the completely assembled unit and terminal panel mounted in a protective housing;

Figs. 6, '7 and 8 are partlydiagrammatic views showing how various control connections may be made on the control panel; and

Fig. 9 is a diagrammatic view illustrating a housing especially adapted to enclose the photocell, the light source, and all the connections thereto which may be permanently arranged.

Referring more specifically to Fig. 1 of the drawings, the apparatus comprises a direct current tube I of the heater type which is energized from an alternating current supply to actuate an electro-responsive device 2 such as a relay in response to light fluctuations impinging upon a photo-cell 3. The tube I comprises a control grid 5, an anode plate I, an electron emitter 8 and a heater 9 and it is energized from the terminals LI and L2 which are connected to any convenient alternating current service line.

In accordance with my invention, I provide a Voltage multiplier for applying independently rectified direct' current voltages to the plate and the grid, each of which may be of a greater magnitude than the average line voltage.

The voltage multiplier comprises a pair of condensers CI and C2 and a vacuum tube rectifier I I, of the type now on the market as type 25Z5. This rectifier has two separate anodes I2 and I3 having respectively associated cathodes I4 and I5. In my system one of the anodes I2 is connected by suitable conductive means II directly to the line terminal LI. Two rectifier cathode heaters I8 and I9 are connected in series across the line terminals LI and L2 through a circuit including a series resistor RI and the tube heater 9, which is shunted by a suitable resistor R2 since it does not require as much current as the rectifier cathodes. This circuit may be traced from terminal LI by way of conductors I1 and 2|, resistor RI, the rectifier cathodes I8 and I9, conductor 22, the tube heater 9 and resistor R2 in parallel, thence by way of conductor 23 to the other line terminal L2. The electron emitter I4 of the rectifier adjacent the upper anode I 2 is connected to the tube anode plate 1 through the coil of the relay 2 to be controlled and it is by-passed to the conductor 23 and the other line terminal L2 by a condenser CI. The lower rectifier anode I3 is connected by a conductor 25 through a grid biasing potentiometer resistor R3, thence through the conductor 23 to the line terminal L2. Series resistors R may be provided on either side of the potentiometer resistor R3.

The grid biasing potentiometer resistor R3 is by-passed by a suitable condenser C2 and the sliding contactor 26 is connected by a conductor 21 through a suitable series resistor R4 of high resistance to the control grid 5 of the amplifier tube. The electron emitter l5 which is associated with the lower anode l3 of the rectifier II is connected to the line terminal Ll through suitable conductors 2| and I1.

The photo-cell 3 or high resistance contacts to control the device may be connected directly between the control grid 5 and the anode plate I of the tube. A light source 3| for influencing the photo-cell may be connected across the line terminals LI and L2 in any suitable manner.

The operation of the apparatus shown in Fig. 1 may be set forth as follows: When the supply conductor LI is negative with reference to the supply conductor L2, an electronic current flows from the cathode I5 to the plate l3 charging the condenser C2. Similarly, when the supply conductor L2 is negative with reference to the supply conductor LI, an electronic current flows from the cathode I4 to the plate I 2, charging the condenser CI. The charges accumulated by the condensers Cl and C2 in this way are of such polarity that the positive terminal of condenser C2 is connected to the negative terminal of condenser Cl and the potentials of the condensers Cl and C2 accordingly add across their outer terminals. Assuming that the resistance of the condenser charging circuits is negligible, and that no load is drawn from the condensers CI and C2, these condensers will be charged to the peak value of the impressed electromotive force during the first cycle. For example, if the voltage of supply conductors LI and L2 is 115 volts effective, and the voltage wave form is sinusoidal, each condenser CI and C2 will be charged to 115 1L41 or 162 volts, and the total voltage across condensers CI and C2 in series will be 324 volts. This voltage cannot be permanently maintained in the circuit shown, because of the drain on the condensers Cl and C2 caused by the load current. However, it is comparatively easy to maintain a direct-current voltage of 250 to 300 volts with condensers of reasonable size.

The voltage across the condenser C2 is divided by the resistors R and R3 acting as a potentiometer, so that the grid 5 is biased negatively with reference to the cathode 8 to a suitable potential. The charge on the condenser CI provides a positive voltage for the anode or plate I, with reference to the cathode 8.

If the photo-cell 3 becomes illuminated, it permits an electronic current to flow through the resistor R4 to the plate I. The IR drop in the resistor R4, under these conditions, opposes the negative bias supplied by the resistors R and R3, and the grid 5 passes through the critical potentie] at which anode current is initiated, into a positive potential range. An electronic current, accordingly, flows from the cathode 8 to the plate I, causing operation of the relay 2. It will be noted that the anode current flows in a path independent of that traversed by currents supplying the grid 5. The grid potential is, accordingly, unaffected by variations of plate current.

Long control leads may be used and they may be in a conduit because the plate and grid circuits are energized by direct current and capacity effects do not interfere with the operation. In some installations the control leads have been successfully extended to fifty feet. The device can also be operated on alternating current of any frequency at 115 volts. By proper adjustment of the potentiometer the desired operation and degree of sensitivity may be obtained.

In the system shown in Fig. 2 a simple arrangement is provided which may be very conveniently adapted either to pull up or drop out the relay on either make or break. This is accomplished by providing a series resistor R5 in series with the connection 25 extending from the rectifier anode plate to the negative end of the potentiometer resistor R3. A conductive connection is provided from the negative end of the potentiometer resistor R3 to a control terminal A provided on a panel adjacent the other control terminals B and C. The control terminal B is connected through a suitable conductor 36 to the control grid 5 of the amplifier tube, and the terminal C is connected by a conductor 31 to a voltage dividing resistor R6 which is connected in shunt across the condenser CI for providing a positive control potential.

By connecting the photo-cell or other control device across the terminals AB the grid of the amplifier tube will be biased negatively as the impedance of the control device diminishes thereby causing the relay to drop out. If it is desired to cause the relay to pick up as the impedance of the control device decreases, it is only necessary to connect it across the terminals BC thereby applying a positive potential to the grid in accordance with the decreasing impedance of the device.

As shown, the control device or photo-cell may be connected to the amplifier tube through a double pole double throw switch 4|] whereby either operation may be very conveniently selected at will. It will be apparent that many other convenient switching or plug-in arrangements may be utilized if desired.

A time controlling condenser C3 may be connected in shunt with the grid series resistor R4 to provide slow response either pulling up or dropping out. Time delays are often desired, in door operating systems, automatic traffic-light control and the like. By completing the condenser shunt circuit through back contacts b on the relay 2 slow pick up is provided. The condenser is discharged through the front contacts 0 when the relay pulls up and the relay will drop out quickly in response to a variation of the control potential. To provide the slow response on dropping out, the condenser circuit is completed through the front contacts c of the relay and discharged through the back contacts b by rearranging the connections as will be readily understood. For a 10 megohm grid resistor, a condenser C3 of about 1.0 microfarad capacity has a time constant of 10 seconds. By using combinations of condensers controlled by front and back contacts various timed pull up and drop out periods may be provided.

As shown in Fig. 2, the system is adapted to utilize a pentode type amplifier tube the screen grid 42 of which is connected by a suitable conductor 43 to a tap on the voltage dividing resistor R5 for a proper positive bias. An additional tap the photo-cell 3.

on the voltage dividing resistor is connected by a suitable conductor 3'! to the control terminal C to provide a suitable positive control potential for This tap can be conveniently selected to provide a suitable voltage for control by either vacuum or gas filled photo-tubes.

Instead of switching a single photo-cell between terminals AB and BC, two photo-cells may be provided permanently connected, as shown in Fig. 3, whence alternative variation of the intensity of illumination on either cell will cause the relay 2 to pull up or drop out.

As shown in Fig. 3, an auxiliary rectifier may be provided for biasing the screen grid of the amplifier tube. The auxiliary rectifier 5| is connected across the line terminals LI and L2 through a suitable resistor R1 which is by-passed by a condenser C4. The screen grid is connected through a conductor 52 to a point between the auxiliary rectifier 5| and its series resistor R1. The resistor R1 may be properly selected or it may be variable to determine the proper positive bias on the screen grid of the amplifier tube. The heater of the auxiliary rectifier tube may be energized in any suitable manner as by connection to the line terminals through a suitable series resistor R8.

It will be understood that the relay armature may be made to pick up by illumination or by an interruption of light depending upon how the photo-cell is connected to the terminals. If the photo cell is mounted in the unit, terminal D is connected to A, and E to B. If the photo-cell is mounted external to the unit the anode lead is connected to A and the cathode lead to B. The potentiometer is then adjusted all the way clockwise and relay armature will hold up as long as the photo-cell is properly illuminated, and it will remain down as long as the photo-cell is dark.

If it is desired to have the relay armature pull up when the light is interrupted it is only necessary to connect D to B and E. to C and adjust the potentiometer all the way counter-clock- Wise.

The embodiment of my invention shown in Fig. 4 is adapted for excitation from a direct current line. In this system the grid biasing potentiometer resistor R3 is connected across the line terminals LI and L2 in series with a resistor R9 which has a suitable tap connected through a conductor 55 for biasing the screen grid and cathode. The control of this system is quite similar to the systems previously described. In this system a second pentode tube is preferably connected in parallel with the first in a manner readily understood by those skilled in the art.

The direct current modification may also be arranged to pull up the relay armature or to cause it to drop out upon either illuminating or darkening the photo-cell depending on how the photo-cell is connected.

If it is desired to pull up the armature by illumination when the photo-cell is mounted in the unit terminals D should be connected to A, and E to B. If the photo-cell is mounted external to the unit, connect the anode lead to A and the cathode lead to B. The photo-cell should then be darkened by completely shielding it from light. The potentiometer should then be turned clockwise slightly beyond the point where the armature just opens. The relay armature will now stay up while the photo-cell is illuminated and it will drop out when the light is interrupted.

If the other operation is desired change the photo-cell connections to terminals B and C and adjust the potentiometer first to open the relay armature and then in the opposite direction slightly beyond the point where armature closes.

In Fig. 5 the completely assembled unit is shown with the photo-cell 3 and terminal panel 55 mounted in a protective housing. The control terminals ABC are arranged in convenient sequence on the panel 55 under the photo-cell terminals D and E. The line terminals Li and L2 are mounted on the opposite end of the panel and the relay controlled terminals 51 and 58 are disposed adjacent the upper edge. A screw driver slotted shaft 59 extends through the panel 56 for conveniently adjusting the potentiometer. An aperture 60 in the door 6| of the housing admits light for controlling the photo-cell if the latter is to be mounted in the housing.

On alternating current, whenever the photo tube or contact cable is run in conduit, the conduit should be electrically connected to terminal L2. If both sides of the alternating current line are at a voltage above ground, it is not possible to use an extended photo-cell or contact except by providing a 1:1 insulating transformer between the LE line terminals and the supply line.

In Fig. 6 I have shown how an automatic hold in may be accomplished by a lamp 63 which is controlled by the relay 2. When a fiash of light from the remote source 64 causes the relay 2 to operate it energizes the associated lamp 63 which then illuminates the photo-cell 3, directly or by reflection from a mirror 65, for accentuating the impedance variation which caused the relay 2 to operate. The relay will then continue to hold in until the light from the associated lamp 53 is interrupted.

A photo-cell 3 and a microphone 61 may be arranged, as shown in Fig. '7, to pull up the relay 2 and drop it out.

The system shown in Fig. 8 provides an interesting demonstration whereby a lecturer may light the electric lamp 63 by means of a match 68 and blow it out by breathing upon the grid 69. The breath responsive grid 69 may be made by drawing two interlaced grids on a heat resisting glass plate 10 with liquid platinum (which is a mixture of finely ground platinum and solvent) and baking off the solvent.

The difiiculty and expense of mounting and connecting a photo-cell 3 and a special source of light 12 at a distant point may be entirely avoided and these elements may be permanently mounted and connected within a housing 13, as shown in Fig. 9. A suitable opaque enclosure 14 in the housing must be provided for shielding the photo-cell 3 from the direct light from the lamp l2. Openings or Windows 15 in the housing permit a beam of light to be transmitted from the lamp I2 to a reflecting surface 16, preferably focusing, from which it is reflected to the photo-cell 3 also within the housing 13. Interruption of the light beam will cause the relay to operate in the manner previously set forth. By selecting a lamp 12 of proper current capacity, it may be energized in series with the heater and cathodes of the amplifier and rectifier tube thereby eliminating the series resistor RI and the consequent waste of electrical energy.

It will be apparent that I have provided a lightcontact relay which can be operated on any frequency alternating current at 115 volts, wherein the photo-cell leads may be extended to fifty feet if necessary, which may be conveniently adjusted for fast or slow action on breaking or making the light beam, and which uses no telephone relays but which applies microamperes to control a 20 ampere contactor directly. As above set forth either vacuum or gas-filled photocells can be used and a terminal panel is provided which allows the operator to obtain relay make contact in response to either making or breaking the light beam.

I am fully aware that many modifications are possible and my invention is not to be restricted except insofar as necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In a light relay, an amplifying discharge device having an anode, a cathode and a control electrode effective at a predetermined potential to initiate a discharge between said anode and cathode and effective at a given potential more negative than said predetermined potential to prevent such discharge, a photo-electric element effective to pass a current under predetermined conditions of illumination, potential supply means for said discharge device including an anode connection, a first tap for supplying a bias potential to said control electrode, said tap including a resistance element, a second tap for providing a potential more positive than said predetermined potential, and a third tap for providing a potential more negative than said given potential, manually adjustable means for selectively connecting said photo-electric element between said first and second taps or between said first and third taps, and a translating device included in said plate connection.

2. In a light relay, an amplifying electric discharge device having an anode, a cathode and a control electrode, potential supply means for said discharge device including a cathode connection, a direct-current bias connection and a positive direct-current connection with reference to said bias connection, a photo-electric element effective to pass a current under predetermined conditions of illumination, resistance means, capacitance means, means connecting said photoelectric element between said positive connection and said control electrode and means connecting said resistance means and capacitance means in parallel between said bias connection and said control electrode, whereby upon passage of a predetermined current through said photo-electric element, said control electrode attains its final positive potential after a time delay.

3. In combination in an electronic control apparatus a screen grid type electric discharge device having an anode, a cathode, a control grid and a screen grid, electro-responsive means to be controlled, an anode energizing circuit for said device including said electro-responsive means, a resistor connected between the cathode and the anode energizing circuit, a tap on said resistor connected to the screen grid, a control grid biasing resistor having a. tap connected to the control grid, means conductively connecting one end of said control grid biasing resistor to the cathode, and means energizable from a source of alternating current for applying independently rectified voltages to the anode energizing circuit and the control grid biasing resistor.

4. The combination in an electronic control apparatus of an electric discharge device comprising cathode, anode and control electrodes, 9. control electrode biasing resistor, a relay to be energized in accordance with the anode current in said device, variable impedance means responsive to a variable quantity or condition, means for connecting said variable impedance means between the control electrode and either the anode energizing circuit or a negative potential point on said biasing resistor whereby operation of the relay may be conveniently selected to pull up or drop out when a given variation occurs.

5. The combination in an electronic control apparatus of an electric discharge device comprising cathode, anode and control electrodes, a control electrode biasing resistor, a relay to be energized in accordance with the anode current in said device, a terminal panel associated therewith, three selective control terminals thereon connected respectively to the control electrodes, the anode energizing circuit and a negative point on the biasing resistor whereby an external controlling device may be conveniently applied to cause the relay to pull up or to drop out when a given variation occurs.

RICHARD C. HITCHCOCK. 

